CDP: application of focus drilling

S. Geisler; J. Bauer; U. Haak; K. Schulz; G. Old; E. Matthus

doi:10.1117/12.835204

27 May 2009 CDP: application of focus drilling

S. Geisler, J. Bauer, U. Haak, K. Schulz, G. Old, E. Matthus

Proceedings Volume 7470, 25th European Mask and Lithography Conference; 747015 (2009) https://doi.org/10.1117/12.835204
Event: 25th European Mask and Lithography Conference, 2009, Dresden, Germany

Abstract

The achievement of a depth of focus required for stable process conditions is one of the biggest challenges in modern optical photolithography. There are several ways of improving the depth of focus. For line/space layers, for instance, application of RET (Resolution Enhancement Technology) using scattering bars, phaseshift masks or optimized illumination systems have shown good results. For contact and via layers the depth of focus is limited and critical, due to the structure size of the holes, alternating pattern density and wafer topology. A well known method of improving the depth of focus for contact and via layers is called focus latitude enhancement exposure (FLEX) [1-3]. With FLEX, several focal planes are being exposed, i.e. each during a separate exposure step. The main drawback is low throughput, as the total processing time rises which each additional exposure. In this paper, we investigate Nikon's CDP (continuous depth of focus expansion procedure) [4]. The CDP option is applicable to modern scanning exposure tools [4-5]. A schematic view of the procedure is shown in Fig. 1. The CDP value or CDP amplitude defines the tilt of the wafer and thus the range of focus in the resist, as the focus plane migrates through the resist during the exposure. The main advantage of CDP, compared to FLEX, is higher throughput, since focal planes are defined within a single exposure. A non-CDP exposure may result in varying aerial images within resist thickness, therefore leading to decreased image contrast within out-of-focus planes. As shown in Fig. 1 the averaged aerial images of a CDP exposure induce better image contrast throughout the resist layer and therefore increase the focus window.

Citation Download Citation

S. Geisler, J. Bauer, U. Haak, K. Schulz, G. Old, and E. Matthus "CDP: application of focus drilling", Proc. SPIE 7470, 25th European Mask and Lithography Conference, 747015 (27 May 2009); https://doi.org/10.1117/12.835204

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available

Members: $17.00

Non-members: $21.00 ADD TO CART

PROCEEDINGS
6 PAGES

DOWNLOAD PAPER SAVE TO MY LIBRARY

GET CITATION

RIGHTS & PERMISSIONS

Get copyright permission Get copyright permission on Copyright Marketplace

KEYWORDS

Semiconducting wafers

Optical lithography

Photomasks

Resolution enhancement technologies

Critical dimension metrology

Lithography

Tolerancing

Show All Keywords

Keywords/Phrases

Search In:

Publication Years